An ant colony can start with a single queen who must do all the work to excavate her nest, forage and care for and feed her brood. After the brood is mature, they assume the colony tasks. From a single queen, a colony can expand to encompass tens of thousands of workers. Many researchers note that the energy used per ant decreases as colony size increases. This phenomena seems to hold true for many other social groups.
Why are larger groups more efficient? Can the answer to this question improve efficiency in human society? Ants are a useful group to study questions of size and energy use because they can vary of many orders of magnitude and rearing them is possible within the bounds of available resources. For these reasons, ant have been the subject of much of the empirical work on the use of energy at different scales.
Jennifer H. Fewell & Jon F. Harrison. Scaling of work and energy use in social insect colonies. Behavioral Ecology and Sociobiology. pp 1-15.